Manufacture of drawn glass



u Patented Aug. 18, `1942.V u

'r OFFICE MANUFACTURE or DRAWN GLAss Charles F. Wood, Jeannette, IPa., assignor rto American Window Glass Company, Pittsburgh, Pa., a corporation of Pennsylvania Y 9, 193s, seria-1 No. 241,311

Application November 1 y 4 Claims.

i manufacturing drawn glass shown and described in the copending application of Pete Magrini, Serial No. 205,959, filed May 4, 1938, which issued as Patent No. 2,246,053 June 1'7, 1941.

In the aforesaid copending application there is shown and described a method and apparatus whereby glass may` be continuously drawn Vfrom a bath of molten glass without the presence therein of any substantial amount of the waves and batter which have-beencharacteristio of drawn glass for many years. As set forth in said application this result is accomplished by prol viding a transverse flow of air along the meniscus of the rising glass sheet from one edge thereof to the other edge thereof and in the same directionon both faces of the rising glass sheet. In the carrying out of the method disclosed in said application it is desirable V-to' provide and maintain a very uniform flow of the gas along the meniscus and to prevent any substantial iiow of the gases being circulated along the.meniscus from passing-vertically along the faces of the rising glass sheet. Where any substantial amount of the gas being circulated is not carried from `one edge of therising glass sheet to at least the other edge of the rising glass sheet and Apasses vertically along the sheet, there is a substantial tendency for this rising gas to create waves in the iinishedproduct. Furthermore, where the flow is not of a uniform character and substantially all turbulence eliminated, the irregular or turbulent iiow of the gas may result in the formation of what is known as batter inthe iinished product.

By the present invention I provide a method and apparatus whereby a more uniform ow of gas along the meniscus of the rising glass sheet is obtained and whereby the gasbeing circulated is more effectively prevented from rising along the glass sheet between the edges. These objects are accomplished by. the provision of a laminar flow of uthe gas just before it passes along the meniscus or'transversely of the rising glass sheet adjacent the meniscus. Such a laminar ow sumcient to materially reduce turbulence and to cause the gas being circulated to better stay down at or adjacent the meniscus, can be obtained by' providing a plurality of relatively small tubes on i the air inlet side of the rising glass sheet and causing at least a portion of the circulated air or gas -to pass therethrough,

In the accompanying drawing I have shown for purposes of illustration only a preferred embodiment of my invention.

In the draWing-' Figure l is a section through a drawing pit em bodying apparatus which I provide;

Figure 2 is a horizontal section through the drawing pit shown in Figure 1;

Figure `3 is a plan view of a tunnel employed for supplying the gas tothe pit to be circulated therein; i

Figure 4 is a side elevation of the tunnel shown in Figure 3; and

Figure 5 is an end view of the tunnel shown in Figures 3 and 4. f

As shown in the drawing, the molten glass in lthe bath B is fed to the drawing chamber 2 through a canal 3, the drawing chamber 2 being separated from the canal 3 by means of a bridge wall. A oater or debiteuse 5 is positioned in the drawing chamber Zand is provided with a longitudinally extending slot 6 through which ythe -glass sheet S is drawn. The floater or debiteuse 5 is held partially submerged in the glass bath by appropriate presser bars (not shown) which cooperate with the four corners thereof. `The glass wells upwardly through the slot in the iloater and is' initially started vertically by `means of a bait.' The glass sheet S passes upwardly through the drawing chamber 2 between the socalled 49-blocks 1 and between the -longitudinally extending angles 8, which are positioned adjacent opposite faces of the rising glass sheet, and then passes into the .base of the vertically extending lehr 9. As is well known in the art, the lehr is provided with a plurality of pairs of rolls lil which carry the sheet verticallyv therethrough. The lehr 9 is a cooling lehr and is of suiiicient length topermit cooling of the glass sheet to a point Where it can be manually handled. Adjacent the top of this lehr the rising glass sheet is cut into smaller sheets and these smaller sheets are then taken to the cutting room for further cutting.

The drawing chamber is provided with a pair of main coolers Il which are located adjacent fthe meniscus I2 of the rising glass sheet, one'f-of.` said and are iso arranged as to be movable toward or away from the risingglass sheet in accordance with the prevailing operating conditions. Appropriate conduits I3 are provided for supplying cooling fluid to the coolers and similar conduits I4 are provided for discharging the cooling fluid from the coolers after it has been circulated therethrough. In accordance with the invention described and claimed vin Monro Patent No. 2,002,544, a pair or auxiliary coolers I5 are located in the drawing chamber above the main cooler. 'I'hese coolers4 are, in general, smaller than the main coolers but are similar thereto and are positioned on each side of the rising glass sheet and extend longitudinally of the drawing chamber` throughout at least the width of the sheet. Conduits I6 are provided for supplying cooling uid to the coolers I5 and conduits Ilare provided for discharging the cooling fluid therefrom.

Preheated gas is supplied to the drawing chamber at one end thereof by a tunnel I9 resting on the adjacent bridge wall 20. The inlet end of the tunnel is positioned exteriorly of the drawing chamber and this end is open so as to receive either atmospheric air or any other gas which may be fed thereto. A g'ate 2| is mounted in this end of the tunnel for regulating the ow of gas therethrough. An electric heating element 22 is mounted in the tunnel adjacent the inlet end for preheating to a suitable temperature the gas which is to be fed into the drawing chamber. The discharge end of the tunnel I9 is positioned 'discharge end of thefork in which they are mounted and extend toward the inlet opening through the tunnel I9 enters in a plurality of of the tunnel a sufficient distance, preferably in the neighborhood of 10 inches, to break up the normal flow vof the gas through the forks and to provide a plurality of small streams of air entering the drawing pit. i

The air which passes into the drawing pit the elimination of turbulence is brought about a by reason of the fact that the air velocity is more in the drawing chamber. This end of the tunnel is preferably forked so as to provide for the discharge of the preheated gas on oppositey faces of the rising glass sheet and the discharge openings are located adjacent the meniscus so that a relatively uniform flow of the gas along the meniscus and between the coolers and the rising glass sheet can be obtained. Satisfactory results can be 0btained where the discharge end of the tunnel I9 is positioned above the meniscus but best results 'of the inlet tunnel except for the dierence pointed out hereinafter. These forks likewise preferably project inwardly a short distance bcyond the edge of the rising glass sheet and are therefore spaced apart a suicient distance to receive theedge thereof. The tunnel 24 rests upon t-he breastwall 26 on the discharge or exit end of the drawing chamber. lThe discharge end of the tunnel 24 is located outside the drawing chamber and is connected by a suitable conduit 21 to an `exhaust fan 28 driven by a motor 29. The discharge outlet 30 of the exhaust fan preferably'extends through the floor and is connected with' the main exhaust system of the factory so as to prevent the discharge of the hot gases into the area adjacent the drawing chamber.

.-i.Ihe-forks 23 of the-inlet vtunnel I9 each have azpluralityof small tubes 3,I positioned therein. Acsuilicient number of these small tubes (which are fpreferably approximately about one-half inch ber.

uniform than it would be if the tubes are not used. The gases pass substantially straight across the sheet along or adjacent the meniscus and enter the discharge tunnel 24. In addition j to the elimination of turbulence, the use of the tubes 3l through which the gas enters the pit has the effect of keeping the transversely flowing current of air down closer to the meniscus of the glass sheet and prevents it from rising up along the sheet.

Substantially horizontally extending shields 32 are located above each of the main coolers. These shields extend longitudinally of the drawing chamber throughout the 'width of the rising glass-sheet. One end of each shield 32 is supported on the upstanding leg of a heat distributing and cooling retarding angle 33 and the other end thereof is supported on the top of the adjacent cooler and extends inwardly of the cooler toward the rising glass sheet. These shields in conjunction with the coolers provide a passageway through which the transverse circulation of the gas is effected adjacent the meniscus. These shields aid in preventing stray gas currents from striking the rising glass sheet adjacent the meniscus and reduce the amount of air or gas being circulated which mayescape upwardly along the rising glass'sheet. Where only theshields are employed and the tubes which I provide by the present invention are not used some of the gas will rise along the glass sheet in view of the fact; that the Ashields are spaced from the rising glass sheet. [The quantity of gas which does rise along the glass sheet at this point is very substantially reduced by the use of the tubes. y

The heat distributing and cooling retarding members 33 are angles which extend longitudi- ,nally throughout substantially the entire length of the drawing chamber. These angles aid in the distribution of the heat in the glass in the drawing period.- The angles 33 are mounted on the' breastwall a short distance above the glass bath and above the debiteuse. However, they may be placed in various positions in the drawing cham- For example, they may be placed on the glass bath or on the debiteuse.

In the structure shown vin the drawing various operating conditions may be employed. Highly desirable results may be obtained if the entering gas, after it has passed the heater, is at approximately 370 F. Where the incoming gas 'is ai; approximately this temperature the-tem- E perature `of the outgoing gas is generally approximately 540 F. Careful control of the teml inches of water.

amas?? air or gas which is fed to the chamber and lcirculated along the meniscus. Desirable results can be obtained where the volume of e'ntering gas is from approximately to 30 cubic feet per minute and where the volume of the outgoing gas is approximately 275 lcubic feet per minute. 'Ihe amount of gas fed to the drawing chamber and the amount exhausted therefrom may be appreciably varied. Itis desirable, however, to circulate a substantial quantity of gas adjacent, the meniscus at a relatively low-l velocity. If too small a volume is circulated, or if the gas is circulated at-too high a velocity, there will be greater opportunity forI the formation of eddy currents whichvwill detrimentally aifect the character of the product.

Where preheated gas is utilized some diillculty may be encountered in the bowing or warping j of the rising 'glass sheet. 'I'o prevent this, longitudinally extending pipes 40 are located in the-base of the lehr on opposite faces of the rising glass sheet. Each of these pipes I! has a longitudinally extending slot Il therein fof a length substantially equal to the width of the rising glass sheet. The'pipes and the slots are I claim: y 1 l. In the methodof forming a glass sheet by continuous drawing from .a chamber containing a bath of molten glass, the steps comprising forming the sheet by drawing it vertically from the bath, supplying a gas in a plurality of closely positioned, relatively small streams to positions in the drawing chamber adjacent each face of the rising glass sheet and adjacent the meniscus thereof, and circulating the gas thus 4Supplied to` each face in contact with the faces of the glass sheet transversely of the sheet adjacent the meniscus.

2. In the method of forming a glass` sheet by continuous drawing from a chamber containing a bath of molten glass, the steps comprising forming the sheet by drawing it vertically from the bath, introducing a plurality'of closely positioned streams'of pre-heated gas into said chamber adjacentthe meniscus ofthe rising glass sheet and adjacent each face thereof, and circu4 lating the gas thus supplied to each face transversely cf theglass sheet from one edge to. substantially the other edge adjacent the meniscus .and in the same direction on both faces of the sheet.

so positioned that the slots will discharge a cur- Y tain of air against the rising glass sheet at an angle of approximately One end of each of these pipes is capped and the other end extends` out of the lehr and isconnected to a blower for 3. In the-method ,of `forming a glass sheet by continuous drawing from a bath ofmolten glass,

the steps comprising forming the sheet by drawing it vertically from the bath, supplying a gas t0 the chamber on each side of the glass sheet land supplying air, preferably at atmospheric temperature and at a pressure of approximately .The product obtained by the use of the present invention is superior to that heretofore produced.` The employment of the present invention mate..

rially aids in reducing batter and waves to a minimum.

It will be' understood'that my invention is not limited to the particular apparatus disclosed in` the drawing. The laminar flow may be obtainedy in various other ways and my invention may be applied to machines of various diil'erent types and .to machines embodying only a ,portion of the auxiliary apparatus described above and shown in the drawing as employed in the ordinary Fourcault operations. Furthermore, my invention is not limited to the Fourcault method of drawing glass as it maybe appliedto any of the various types of apparatus heretoforev adjacent one end of the meniscus thereof in a plurality of relatively small, closely positioned streams, and circulating the gas thus introduced invcontact with the faces of the glass sheet from one edge thereof toward the other edge'thereof adjacent the meniscus while shielding the circulated gas from ingress of stray gas currents' and from egress of the circulatedgas from adjacent the meniscus during its travelacross the 4. Apparatus for-drawing sheet glass comprising a drawing chamber having a bath of molten rising sheet.

, glass therein, means for drawing a continuous sheet of glass vertically from the bath, means including two setsof closely arranged conduits for supplying a gas in a plurality of small, closely positioned streams" to said drawing chamber on each face 0f and adjacent the meniscus of the rising glass sheet, and meansfor circulating the gas so fed to each face of the sheet transversely of the rising sheet adjacent the meniscus.

CHARLES F. WOOD. 

